Shredder for sheet material having an improved feeding mechanism

ABSTRACT

A shredder for sheet material comprises a shredding mechanism and an air feeding mechanism. Conveniently the air feeding mechanism comprises a vacuum pump. An air flow path extends through the shredding mechanism of the shredder and the pump is disposed after the shredding mechanism in the air flow path. The air feeding mechanism comprises a collection device for collecting shredded particles, which may include a permeable bag.

BACKGROUND TO THE INVENTION

[0001] This invention relates to improvements in feeding mechanisms. Inparticular, this invention relates to improvements in feeding mechanismsfor sheet materials, such as paper, which are fed into a device, such asa shredder, for processing therein. These mechanisms are describedhereinafter in relation to paper, but it will of course be appreciatedthat they could be used with many different types of sheet material.

DESCRIPTION OF THE PRIOR ART

[0002] Typically, in shredders, cutting discs are provided whichthemselves intermesh. Since these are mounted on rollers which rotate inopposite directions, they provide a nip into which paper can be fed, anddraw paper through the shredder without the need for any further feedingmechanism. There are shredders, however, which operate on a differentprinciple, for example the shredder described in pending U.K. PatentApplication Serial No. 0210599.7, in which sheet material is shreddedusing rectilinear punches.

[0003] Typically feed rollers are used in such shredders to feed thepaper into the shredding mechanism. The rollers are situated just beforethe shredding mechanism in the feed path of the paper, but, even so,when the edge of the paper leaves the rollers there is a small amount ofpaper left above the shredding mechanism which is not fed through. Thisproblem can be minimized by siting the feed rollers as close as possibleto the shredding mechanism, and by using gravity to assist the feed ofthe last part of the paper, but these solutions are not whollysatisfactory.

[0004] There is, therefore, a need for a continuous feed mechanism whichcan feed an entire piece of paper through such mechanisms.

SUMMARY OF THE INVENTION

[0005] According to this invention there is provided a shredder forsheet material comprising a shredding mechanism and an air feedingmechanism.

[0006] Use of an air feeding mechanism enables the sheet material to befed completely through the shredding mechanism. The mechanism also hasadvantages in that the sheet material tends to stretch or crinkle lessthan when using a conventional mechanism. The air feeding mechanism alsodraws dust generated by the shredding process through the shredder whereit is less likely to present a health hazard.

[0007] Preferably the air feeding mechanism comprises a suction means,which conveniently comprises a vacuum pump. Conveniently the pressuregenerated by the suction means is greater than 0.5 bar, preferablygreater than 1 bar.

[0008] Conveniently an air flow path extends through the shreddingmechanism, the suction means being preferably disposed after theshredding mechanism in the air flow path.

[0009] Preferably the air feeding mechanism comprises a collection meansfor collecting shredded particles, which conveniently comprises apermeable bag. Conveniently the collection means, or a furthercollection means, is also suitable for collecting dust generated duringthe shredding process.

[0010] Preferably the air feeding mechanism comprises a plurality ofintermediate chambers disposed in the air flow path after the shreddingmechanism and before the collection means.

[0011] Preferably the shredder further comprises feed rollers, which areconveniently located in the air flow path before the shreddingmechanism. These assist the initial feeding of the sheet material.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] An embodiment of the invention will now be described, by way ofexample only, with reference to the accompanying drawing in which:

[0013]FIG. 1 shows schematically a section view of one embodiment of ashredder according to this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014] The shredder 10 comprises a shredding mechanism 12, an airfeeding mechanism 14 and infeed rollers 16. In this embodiment theshredding mechanism comprises a plurality of punch members 18 positionedin die members 20. The mechanism is generally as described in pendingU.K. Patent Application Serial No. 0210599.7, and only the feedingmechanisms will be described further herein.

[0015] Air feeding mechanism 14 comprises a vacuum pump 22 which isconnected by tubes 24 to a collection chamber 26 which contains a paperbag 28 which functions as a collection bag for shredded particles. Tubes30 connect the collection chamber to two smaller chambers, manifolds 32,34. Each manifold 32, 34 is arranged at the outlets of aperture channels36, 38, which receive punch members 18 when in their advanced position.

[0016] The air flow path through the machine will now be described. Airis drawn as shown by arrows X through a feed channel 40 in the diemembers 20, which also acts as an inlet for paper 39 being fed to theshredding mechanism 14. From the feed channel 40, when the punch members18 are in their retracted position, as shown in FIG. 1, air flowsthrough the aperture channels 36, 38 to the manifolds 32, 34. Thesemanifolds 32, 34 provide a convenient way of connecting the manyaperture channels 36, 38 in the die members 20. Air flows from themanifolds 32, 34 to the paper bag 28 in the collection chamber 26, andthrough the paper bag 28 to the vacuum pump 22.

[0017] When the punch members 18 are in their advanced position theyextend past the feed channel 40 into the aperture channels 36, 38 andsubstantially prevent air flow through the air feeding mechanism 14.

[0018] To operate the shredder 10 a plurality of paper sheets 39 is fedinto the shredding mechanism through infeed rollers 16. These rollers 16provide the initial feed, transporting the leading edge of the paper tothe feed channel 40. Once in the feed channel 40 the paper is subjectedto a degree of suction pressure, and the high velocity of air in theinfeed channel 40 draws the paper along the air path. The velocity ofthe air increases as the number of sheets of paper increases since thismakes the infeed channel 40 narrower and thus the effectiveness of theair feeding mechanism 40 is retained despite the larger load.

[0019] When the paper reaches the shredding mechanism 14 it is shredded,generally as described in U.K. Patent Application Serial No. 0210599.7.A plurality of small paper particles 42 is thereby generated, which arecarried along the air flow path through the aperture channels 36, 38,the manifolds 32, 34 and the tubes 30 to the collection chamber 26.These then collect in the paper bag 28. Once full the paper bag 28 maybe easily emptied, and the shredded particles 42 disposed of.

[0020] The suction generated by the air feeding mechanism 14 draws thepaper through the shredder 10 and acts as a convenient way of collectingshredded particles 42. The air feeding mechanism can, as shown in theembodiment above, be supplemented by infeed rollers 16, but can alsofunction as the sole feeding mechanism. Unlike infeed rollers the airfeeding mechanism does not tend to crinkle or stretch the paper, butprovides a smooth and effective feed.

[0021] Although described above in relation to a shredder it will beapparent that the air feeding mechanism outlined herein could be used inother devices, for example a printer, where sheet material must be fedpast a processing head.

[0022] In the present specification “comprises” means “includes orconsists of” and “comprising” means “including or consisting of”.

[0023] The features disclosed in the foregoing description, or thefollowing claims, or the accompanying drawings, expressed in theirspecific forms or in terms of a means for performing the disclosedfunction, or a method or process for attaining the disclosed result, asappropriate, may, separately, or in any combination of such features, beutilized for realizing the invention in diverse forms thereof.

I claim:
 1. A shredder for sheet material, comprising: a shreddingmechanism and an air feeding mechanism.
 2. The shredder according toclaim 1, wherein the air feeding mechanism comprises a suction means. 3.The shredder according to claim 2, wherein the suction means comprises avacuum pump.
 4. The shredder according to claim 2, wherein the suctionmeans generates a pressure which is greater than 0.5 bar.
 5. Theshredder according to claim 4, wherein the pressure generated by thesuction means is greater than 1 bar.
 6. The shredder according to claim2, wherein an air flow path extends through the shredding mechanism, andwherein the suction means is disposed after the shredding mechanism inthe air flow path.
 7. The shredder according to claim 1, wherein the airfeeding mechanism comprises a collection means for collecting shreddedparticles.
 8. The shredder according to claim 7, wherein the collectionmeans includes a permeable bag.
 9. The shredder according to claim 7,wherein the collection means is also operative for collecting dustgenerated during the shredding process.
 10. The shredder according toclaim 7, wherein the air feeding mechanism comprises a plurality ofintermediate chambers disposed in the air flow path after the shreddingmechanism and before the collection means.
 11. The shredder according toclaim 6, and feed rollers located in the air flow path before theshredding mechanism.